r-soy, as Rapha said, this is a "permutations" problem because the order is important- if you bet on a horse to win, his coming in second doesn't help you at all!

As far as (1) is concerned, I don't see how any "explanation" is needed. You are asked to use a calculator to do a specific calculation. Exactly how you would do that depends on what kind of calculator you have. What did you get when you tried it?

For (b), the simplest thing to do might be to multiply the given matrix by each of the possible answers- which one gives the identity matrix? (You can skip (b), it has determinant "7" while the initial matrix and all other answers have determinant "1".)